The District of Columbia housing director proposed yesterday that certificates that permit the future conversion of 8,000 apartment units into condominiums be canceled.

Those certificates were granted before the City Council imposed a still-existing moratorium on most conversions last May, but have not yet been used. Cancelling them would allow the city to "start with a clean slate" after the council adopts a permanent condominium law and the moratorium ends, Robert L. Moore, director of the D.C. Housing Community Development Department, told a council hearing.

Many landlords have sought and received certificates for speculative purposes "with no intention of actually converting the property," Moore testified. He said these landlords "were trying to buy insurance for the future with increased property values but . . . tenants in these properties are totally unsure of their future."

Speaking for Mayor Marion Barry, Moore also urged that people over age 62 with individual income below $13,500 be given a lifetime right to rent their apartments when the buildings are converted to condominiums.

Tenant spokesmen testifying at the hearing insisted that lifetime rental rates should be granted to older residents without regard to income.

The testimony came at an all-day hearing by the council's Housing and Economic Development Committee that focuses on proposed legislation that would tightly control future conversions.

Sponsored by nine of the council's 13 members, the measure would require a majority vote of tenants in an apartment building before an owner could convert. It spells out several other protections for tenants. The committee took no action after yesterday's hearing.

Condominium conversions have become a major political and social issue, with tenants -- notably pensioners with modest incomes -- voicing alarm at the time of conversions forcing them to move or buy units. Landlords in turn contend that their property rights, including those of conversion, are being breached.

The current moratorium imposed last May is still in effect and under current city law will end next August, when it may be replaced by some version of the legislation now being considered.

And expected direct confrontation between tenants and the real estate industry was averted when a spokesman said the industry would "decline to make detailed comment on a series of proposals that persist in . . . shifting more and more of the burden to the producers and operators of housing."

The spokesman, realty executive Kenneth J. Luchs, said the community must "recognize this industry as a partner rather than a culprit." He said the industry will offer a package of proposals later.

Nearly 70 witnesses testified for a total of seven hours yesterday, and most represented community and tenant groups solidly supporting the proposed bill.

"There simply isn't sufficient housing available at any price," said Stuart L. Knoop, speaking for the D.C. Commission on Aging.

Michael Williams, director of the Capitol East Coalition, said the proposed requirement for a majority 51 percent vote among tenants before conversion should be raised to 60 percent -- "a clear and convincing majority." c

Moore, the housing director, was the first witness, and he offered several proposals while saying the Barry administration would not propose a bill of its own.

He urged that conversions be permitted without tenant approval, as they were before the moratorium, only in higher-income apartment projects. But he proposed that the definition of high income be raised.

Under the formula he proposed, an estimated 8,000 units in the city would be eligible to convert. The formula would define high income units as those with rents now ranging from above $377 for an efficiency to $696 for a unit with three bedrooms or more, contrasted with the premoratorium rent range from $242 to $447. While loer-cost units could be converted as they are now with the approval of tenants, Moore proposed adding teeth to the bill to prevent landlords from coercing tenants into conversion agreements.